Audio effects system and method

ABSTRACT

A method and a system of organizing, arranging and rear-ranging the number and sequential order of audio effects circuit modules by the changing, including inserting, removing, exchanging and interchanging, of said modules providing noiseless, uninterrupted signal flow through a system during each of said changing operations. A preferred embodiment of the method comprises an audio signal processing system which includes a main housing, containing a main circuit apparatus, module-receiving recesses, and modules, fabricated to be received in the recesses, each module having an electronic audio effect circuit which affects the signal in a unique way to provide a different sound output. A plurality of switches and potentiometers lie on either the main housing or the module, and each module has markings indicating which controls are to serve its operation. In order to avoid the generation of spurious signals into the main signal path during the changing of a module, and to maintain the uninterrupted flow of the main signal path through the system, switching means are connected such that the main signal path is noiselessly routed: passing either into and out of a recess and through a module which is fully seated therein, or passing by the recess to the next recess. The modules are inserted and removed producing the quiet appearance and disappearance of the audio effect produced by the module. Panel-mounted switches and foot switches are provided to command bypass of any or all recesses even though the modules are fully seated.

RELATED APPLICATIONS

The present application is a continuation-in-part of copending U.S.application Ser. No. 420,846, filed Sept. 21, 1982, which is acontinuation-in-part of copending U.S. application Ser. No. 150,813,filed May 19, 1980 now U.S. Pat. No. 4,388,490. The present applicationalso makes reference to copending U.S. application Ser. No. 479,869,filed Mar. 29, 1983.

BACKGROUND OF THE INVENTION

Electronic signal processing circuitry has become important in the fieldof audio electronics in the modification of audio signals or theproduction thereof. A wide variety of audio effect circuit designs havebeen developed and are constantly being developed to deliver new andinteresting sounds in live performances, recorded performances, or inthe modification of recorded performances.

These circuits are considered components and often appear on the marketin modular form, equipped to be electrically connected into an audiosystem. When several modules are used at the same time they becomedifficult to handle in that cords or cables must be reckoned with. Amusician using these during a live performance is usually confined tothe number of modules and their sequence that was established in theaudio line at the beginning of his program. Flexibility is at a minimum.

Some systems have the functions of several modules permanentlyincorporated into them, and, in some cases, a switching arrangementallows complete sequencing flexibility; but with more than a fewmodules, the switching becomes complex. Thus, many operators of thesesystems add to their system a desired number of the modular components,and their system becomes a combination of the two methods.

The system and method for which a patent is herein applied is based on anew and different concept with respect to sequencing or changing ofmodules.

SUMMARY OF THE INVENTION

The invention comprises a system and method of organizing, arranging andrearranging the number and sequential order of modularly-housedelectronic audio effects circuits, i.e., audio effects circuit modules,by the changing, including inserting, removing, exchanging, andinterchanging, of the modules, providing noiseless, uninterrupted signalflow through a system during each of the changing operations.

A basic embodiment of the system and method, disclosed in the aforesaidpatent application, comprises an audio signal processing system whichincludes a main housing containing a main circuit apparatus, modulereceiving recesses, and audio effects circuit modules containing any ofa wide variety of audio signal processing circuits, the modules beingreceived in the recesses, so that each module can affect the incomingaudio signal in a unique way to provide a different sound output.

A large number of modules can be easily changed and resequencedparticularly by a performer during a performance, without disturbing thecontinuity of the audio signal being delivered in the performance, andwithout introducing spurious signals into the performance.

Controls for the module circuit, consisting of switches andpotentiometers, may be positioned on the module, or on the main housingimmediately adjacent to and surrounding, at least partially, a recess.Each module has markings identifying its audio effect circuitry andindicating which controls control its operation.

The modules can be shaped in the form of an unopened deck of playingcards, of light-weight, break-resistant plastic, devoid ofprotuberances, devoid of their own otherwise necessary controls, and assuch, be of a minimal cost, compactly storable and portable, as opposedto conventional modules, where housings are normally of heavy gaugemetal, containing their own power supply, their own controls, their owninput and output jacks, and once linked to a system, cannot be relinkedin a different sequential order with the ease and facility provided bythe invention herein, especially during a live musical, or otherwise,performance.

The basic embodiment has electromechanical switches associated with eachmodule recess for connecting input and output signals destined for themodule to the associated recess contact elements only when the module isfully seated, in which the module is farther into a recess than thepoint at which module contact elements and recess contact elements arecompletely mated. When the module is not in the fullyseated position,the switches connect the prospective input and output lines together,electrically passing by the recess.

While this eliminates the noise that would be generated by matingcontact elements, the metal contacts in the electromechanical switchesdo make and break the signal path, providing some practical systemlimitations.

Signal path lines must be shielded and protected from magnetic fields,electric fields, and ground loops. The inclusion of electromechanicalswitches produces design problems in direct proportion to the number ofswitches included. Quality control and reliability problems are createdin that metal contacts can become noisy after use, even though theswitch is still otherwise operable.

Electromechanical switches with metal contacts are certainly the mosteconomical and available way for the operator to control the operationof the system and there is need to use more of them to provide thesystem with more control modes.

A major object of an advanced embodiment of this invention is to utilizeonly electronic switches in the signal path.

An electronic switch is here considered to comprise at least one, threeterminal, semiconductor device. The presence of a prescribed voltage atthe device control terminal causes a very low impedance between thedevice input and output terminals; the absence of said voltage causes avery high impedance between the input and output terminals. Theequivalent result of the use of one such semiconductor device is avoltage controlled, single pole, single throw switch. To make multiplepole, multiple throw, electronic switches, more semiconductor devicesand additional electronic circuitry are used. As long as there is justone control voltage into the assembly, it is here considered anelectronic switch in the singular.

There are three major advantages to the use of the electronic switch inthis advanced version. First is the repeatability of the switchingaction. When the opening and closing of the switch is plotted as afunction of time, in the time domain of milliseconds, the electronicswitch performs with repeatability and the rate of change of state is aroutine design matter. Details such as break-before-make can bepredicted and utilized in a cost effective circuit design. With themetal contact, electromechanical switch, the opening and closing of theswitch, in the time domain of milliseconds, is drastically variable,both for multiple trials of one specimen and between specimens.

The second major advantage of the electronic switch is reliability inoperation. In the signal path, an electromechanical switch would beconsidered a failure when it became noisy when operated, due toexcessive contact bounce and other phenomena. This can occur after use,or operator abuse, and generally does occur before otherwisecatastrophic failure. The reliability of the electronic switch is notaffected by use or abuse, and the failure rate can be approximately fivepercent per million hours of operation.

The third major advantage of the electronic switch is that the signalpath can be isolated from transient noise on the control line byconventional, low-pass filtering. Thus, many, perhaps noisy,electromechanical switches can be used to generate the control signalwhile the signal path is electronically switched, noiselessly andrepeatedly. This, in effect, greatly increases the reliability of theelectromechanical switches that are used.

Another object of the advanced embodiment of this invention is toprovide a panel-mounted toggle switch and an alternate-action footswitch for each module-receiving recess in the system main housing. Theswitches have effect only when a module is fully seated in theassociated recess, and operate conjunctively as follows: when the panelswitch is in the "operate" position, the module is allowed to operatenormally, and operation of the foot switch has no effect; when the panelswitch is in the "foot switch" position, successive depressions of thefoot switch will cause the module to be successively by-passed orallowed to operate normally, by electronic means, just as surely asthough the module were physically inserted into, and removed from, therecess. If the foot switch is not connected or is left in a bypass mode,the panel switch may be used alone to command bypass. This gives theoperator a great deal of needed flexibility in operation as he does nothave to physically insert and remove the module to add or delete theeffect. His hands may be otherwise occupied, and the desired changes maybe quite frequent.

Another object of the advanced embodiment of this invention is toprovide a panel-mounted toggle switch and an alternate-action footswitch for the system. The switches have effect when at least one moduleis in the signal path, and operate conjunctively as follows: when thepanel switch is in the "operate" position, there is no effect on thesystem, and operation of the foot switch has no effect on the system;when the panel switch is in the "foot switch" position, successivedepressions of the foot switch will successively cause bypass or noeffect on all modules otherwise in the signal path. If the foot switchis not connected or the foot switch is left in the bypass mode, thepanel switch may be used alone to command bypass for all modulesotherwise in the signal path. Clearly these switches would only be usedin systems with more than one recess. If there were only one recess, theswitches described earlier would provide identically the same function.These switches provide the operator with the opportunity to bypass allthe modules in the system with only one switch depression.

The novel features of the invention are set forth with particularity inthe appended claims. The invention will be best understood from thefollowing description when read in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective, and partially exploded, view of a basic signalprocessing system housing, constructed in accordance with the presentinvention;

FIG. 2 is a perspective view of part of the system of FIG. 1, showing amodule thereof in a partially inserted position;

FIG. 3 is a section view of the apparatus of FIG. 2, shown with themodule in fully-seated position;

FIG. 4 is a section view of part of the apparatus of FIG. 3, with themodule in a partially inserted position;

FIG. 5 is a section view of a portion of the apparatus of FIG. 4, shownwith the module in a fully-seated position;

FIGS. 6a-6b shows perspective and other views of a module of thisinvention;

FIGS. 7a-7i is a multi-view of a latch-coupled switch, said latch, and au-bracket, all associated with one recess of the system housing of FIG.1;

FIG. 8 is a partial electrical schematic of the apparatus associatedwith one recess of the system housing of FIG. 1;

FIG. 9 is an electrical schematic showing, along with FIG. 8, how amodule bypass switch is connected;

FIG. 10 is a perspective view of an advanced audio signal processingsystem, constructed in accordance with the present invention;

FIG. 11 is a front elevation view of a fully-seated module and a recessframe of the system of FIG. 10;

FIG. 12 is a side elevation view, partly in section, of apartially-inserted module and a recess frame of the system of FIG. 10;

FIG. 13 is a top plan view, partly in section, of a fully-seated moduleand a recess frame of the system of FIG. 10;

FIG. 14 is a section view taken approximately along line 14--14 of FIG.12;

FIG. 15 is a section view taken approxiately along line 15--15 of FIG.12;

FIG. 16 is a section view taken approximately along line 16--16 of FIG.12;

FIG. 17 is an electrical block diagram, partly schematic, of the systemof FIG. 10;

FIG. 18 is an electrical block diagram, partly schematic of electronicswitches included as blocks in FIG. 17;

FIG. 19 is an electrical schematic of an existing art, tone controlcircuit for inclusion in an audio effects circuit module for the use inaccordance with the present invention;

FIG. 20 is an electrical schematic of an existing art, "fuzz" circuitfor inclusion in an audio effects circuit module for use in accordancewith the present invention;

FIG. 21 is an electrical schematic of an existing art, swept audiofilter circuit for inclusion in an audio effects circuit module for usein accordance with the present invention;

FIG. 22 is an electrical schematic of an existing art, tremolo circuitfor inclusion in an audio effects circuit module for use in accordancewith the present invention;

FIG. 23 is an electrical schematic of an existing art, noise gatecircuit for inclusion in an audio effects circuit module for use inaccordance with the present invention;

FIG. 24 is a perspective view of an alternative embodiment of anadvanced audio signal processing system constructed according to thepresent invention.

FIG. 25 is an electrical schematic showing how a recess bypass switch ofthe system shown in FIG. 24 may be connected.

FIG. 26 is an electrical block diagram, partly schematic, of the systemof FIG. 24;

FIG. 27 is a front elevation view of an alternative embodiment of afully-seated module and a recess frame of the system of FIG. 24.

FIG. 28 is a side elevation view, partly in section, of a partiallyinserted module and a recess frame of the system of FIG. 24.

FIG. 29 is a diagrammatic representation of another embodiment of thesystem wherein the recess and audio effects are coupled in parallel; and

FIG. 30 is a diagrammatic representation of another embodiment of thesystem wherein the recess and audio effects are coupled inseries/parallel.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 illustrates a basic audio signal processing system of thisinvention which includes a main housing 1 having module-receivingrecesses 2 designed to receive audio effects circuit modules 3.

The module 3 has embedded in it a multiplicity of module contactelements 20, as shown in FIGS. 3, 4 and 5 which are positioned tocontact recess contact elements 16, upon installation of module 3 intorecess 2. Modules can be constructed with any feasible size, shape andmaterial, with contact elements of any correspondingly feasible size orshape placed in any end, edge or side of the module's housing. FIG. 6illustrates assembly views of module 3, indicating removable sides,placement of the circuit board and its circuit, circuit connecting tocontact elements, and face markings as used herein.

A group of potentiometers and switches 5,6,7,9,10,11,12 are positionedon main housing 1 immediately adjacent to each recess 2, and have all oftheir respective terminals connected only to their respectivepreassigned recess contact elements 16. These controls are not a part ofand have no effect upon said main circuit or system until a module 3 isfully seated in the recess 2. While a module 3 is so fully installed,these controls serve as the controls of module 3, controlling theoperation of its circuit.

Markings on the face of each module 3, as shown in FIG. 6b, identify itsparticular circuit or sound effect, and indicate which of the controlscontrol the module's operation. In one embodiment, when fully seated ina recess, the face of the module is flush with the control panel 30 ofthe main housing 1 and the markings indicate the controls on the controlpanel 30 to be used with respect to the module's circuit and itsrespective control functions. In an alternative embodiment, as discussedhereinbelow, the face end of the module protrudes from the controlpanel.

A recess bypass switch 8, of FIG. 1, is provided at each recess suchthat a module, while fully seated, can be electrically passed by whenthe switch is manually operated.

FIGS. 2, 3, 4 and 5 illustrate the manner in which recess contactelements 16 are mounted and positioned and make contact with modulecontact elements 20. An elastomeric foam slab 17 is positioned on thefront side of the far wall 26 of recess 2. As can be seen in greaterdetail in FIGS. 4 and 5, recess contact elements 16 are positioned andembedded, somewhat, in foam slab 17, so that their pins project throughfoam slab 17 and through their respective guide holes in far recess wall26, retained there by retainers 23, connected via thin, flexible,insulated wires 21 to junction pins 22 which are molded into and projectthrough recess terminal junction panel 18. It is at this panel 18 thatthe main circuit and controls 5 through 12 are connected to recesscontact elements 16. And in this manner recess contact elements 16 haveindividual compressive sliding action through the guide holes.

FIG. 4 further shows recess contact elements 16 before correspondingcontact is made with module contact elements 20. FIGS. 3 and 5 showrecess contact elements 16 in their compressed full contact with modulecontact elements 20 when module 3 is in a fully-seated position.

The main signal path flow routing through the system shown is a basicseries circuit, taking the main signal into and out of a recess 2, andits module 3, and so on, in series, except that when the recess 2 isdevoid of a module 3, then the recess 2, with respect to the mainsignal, is in a bypass state, and when a module 3 is in the recess 2 inany position other than fully seated, the recess 2 can also be in abypass state.

As discussed hereinbelow, the routing through the system may include aparallel circuit of recesses, or a combination series/parallel network.

The input audio signal is accepted at input jack 31. It goes to an inputattenuator or potentiometer 32, and then to a conventionalbuffer-amplifier. The output of the buffer-amplifier goes first to thelowest-ordered recess 2, or passes by it, and so on through or by eachrecess to an output attenuator 33, and then to output jack 34,delivering the modified signal, or an unmodified signal if there is nofully-seated module in the system.

FIG. 7 illustrates the means for the locking-in of a fully-seated module3 in a recess 2, and for the unlocking or freeing of module 3 fromrecess 2. As can be seen, latch 25 encircles the handle of spring-loadedtoggle switch 4 and is held slidably captive by u-bracket 29 against theinner surface of control panel 30. Switch 4 is attached to u-bracket 29so that handle of switch 4 projects through the coupling hole of latch25 and through control panel 30 making the handle accessible for manualactuation. In their simultaneous normal positions, of FIGS. 7b, 7c, 7d,7e, the handle of switch 4 rests laterally against the side of the holein control panel 30, and the quarter-rounded end of latch 25 projectsslightly into recess 2. FIGS. 7f, 7g, 7h, and 7i show the simultaneousmomentary positions of switch 4 and latch 25.

A slight insertion of a module 3 into recess 2 brings latch 25 andhandle of switch 4 to their momentary positions. When module 3 reachesits fully-seated position in recess 2, the latch 25, under the internalspring force of switch 4, via said handle of switch 4, springs back toits normal position, into locking-notch 24 of module 3, of FIGS. 1, 2,3, and 6, holding the module 3 in said fully-seated position in recess2.

A lateral fingertip manipulation of said handle of switch 4 brings saidhandle of switch 4 and latch 25 to their momentary positions, allowingsaid module 3 to be partially expelled by the spring forces of aspring-loaded push button switch 15, as shown in FIG. 2, on recess wall26, and said foam slab 17.

FIG. 8 illustrates the flow of the main signal with respect to a typicalrecess 2 and its associated electrical connections. Switch 4 is a doublepole, double throw, springloaded toggle switch, whose normal position isclosed. Switch 15 is a single pole, single throw, spring-loadedpush-button switch whose normal position is closed.

When a recess 2 is empty, both of the switches 4 and 15 are in theirrespective normal positions, and, as such, switch 15, via switch 4 hasrecess 2 in a bypass state. Input and output lines destined for themodule are connected to the associated recess contact elements 16 ofrecess 2 and are shorted together.

A slight insertion of a module 3 into a recess 2, displaces latch 25which simultaneously displaces switch 4 to its momentary positiondisconnecting input and output lines from the recess contact elementsand shorting the line together. Switch 15 is still in its bypass state.

Upon further insertion, to a predetermined depth of insertion, module 3engages push-button switch 15, displacing switch 15 to its momentaryposition, opening its contacts allowing switch 4 to function in itsmomentary state. Both the input and the output lines, though nowconnected together, are each, respectively, disconnected from recess 2,and its contact elements 16.

A slight but fuller insertion of module 3 brings the initial meeting,the first physical, but not necessarily simultaneous, contact betweenall respective and corresponding module contact elements 20 and recesscontact elements 16. This is a critical point at which spurious signalsmight otherwise be generated into the main signal path were it not forthe fact that switch 4 is in its previously described state.

At a fuller depth of insertion, and after solid physical and electroniccontact has been established between all said contact elements, acompletely mated condition between the module and recess is established,and the fully-seated position of module 3 is reached, at which point, asearlier described, latch 25 springs into locking notch 24, assimultaneously switch 4 changes to its normal position, allowing themain signal to flow into and out of recess 2 through its locked-in andoperating module 3.

Noting the now fully compressed states of switch 15 and foam slab 17, itcan be seen how the foam slab 17 maintains the integrity of contactbetween module and recess contact elements; and foam slab 17 and switch15 conjunctively stabilize module 3 in its locked-in position in recess2, via their respective compressive forces.

The removal of module 3 from recess 2, in the manner earlier described,provides an exact reverse of the sequence of events just described,including the partial expulsion of module 3 from recess 2, via saidcompressive forces.

Though switch 4 and switch 15 are shown as conjunctively actingspring-loaded momentary switches, this is not necessarily required torealize the benefits of the present invention. As shown in FIG. 8a, withthe circuitry of switch 15 removed from the system, and toggle switchbeing a totally manually operated switch, without momentary biasedsprings, noiseless insertion can be accomplished by an operator manuallyoperating toggle switch 4a. In other words, the modules could beinserted into and removed from the recess and the audio signal pathwithout introducing spurious signals into the audio signal path andwhile maintaining the continuity of the audio signal path, if theoperator always kept switch 4a in its bypass position until the modulewas fully inserted into the recess, and again placed switch 4a in itsbypass position before removing the module from said recess.

FIG. 8b illustrates an alternative embodiment of the present inventionwherein the operation may be manually controlled by means of a singlepole double throw switch 4b in lieu of the double throw double poleswitch 4 wherein the audio signal input 13 is connected at all times toterminal 128 and only the main signal output 19 is cut, with the output19 being switchably connected to either terminal 101 to route the signalthrough the module, or connected to incoming signal 13 to bypass therecess.

Potentiometer 14, FIGS. 1 and 8, positioned on control panel 30,functions as a bias control to those of modules 3 whose circuitry designis such that they require variable bias control.

Included in said main circuit apparatus, is a conventional, sectionedand filtered, a.c. to d.c. power supply, feeding the various d.c.potentials to all components as required.

FIG. 9, in conjunction with FIG. 8, illustrates how switch 8 isconnected to enable the operator to pass by a recess even though amodule is fully seated therein. When switch 8 allows the connection ofinput 13 to the recess contact element 16 designated as module input128, and allows the connection of output 19 to the recess contactelement 16 designated as module output 101, the module is active asthough switch 8 were not present. However, when switch 8 connects input13 to output 19, the recess, and thus module, is passed by.

FIG. 10 illustrates an advanced audio signal processing system whichincludes a main housing 41 having module-receiving recess frames 80designed to receive modules 43. The recess next to the recess on theright is shown empty, while the other recesses are shown containingmodules, with the module on the left showing typical markings. Thesystem also comprises a multiple foot switch unit 71 which iselectrically connected to the main housing circuitry by multiconductorcable 66.

The input audio signal is accepted by an input jack at the rear of themain housing. Input level is adjusted with potentiometer 62 and isindicated by the illumination pattern of light emitting diodes 55.Switch 54 provides the option of 180 degree phase reversal from input tooutput. Switch 53 provides the option of using an internal envelopefollower or an externally-supplied, similar control signal. Circuitrynecessary for these controls and indicators are existing art and wellknown in audio equipment.

Potentiometers 45, 46, 50, 51, 52, and switch 47 are positioned on thecontrol panel 70 of main housing 41 immediately adjacent to each recessframe 80, and have all of their respective terminals connected only totheir respective preassigned recess contact elements 88. These controlsare not a part of, and have no effect upon, the main circuit or systemuntil a module 43 is operating in the signal path. While a module 43 isso operating, these controls serve as the controls of module 43,controlling the operation of its circuit. Controls may also be on theface of the module in addition to, or in lieu of, the controls on thecontrol panel 70 as shown in FIG. 24 and discussed in more detailhereinbelow.

Potentiometer 49 adjacent to each recess frame 80 is a level control inthe signal path immediately following the potentiometer's associatedmodule. It is only operative when the module is operative.

Latch-coupled switch 44, adjacent to each recess frame 80, and latch 86lock a module in its fully-seated position and provide the means for theoperator to eject the module.

The operation of the module bypass switch 48, adjacent to each recessframe 80, and its associated foot switch 72, has been described above.The operation of the system bypass switch 58 and its associated footswitch 73 has also been described above.

Light emitting diode 57 adjacent to each recess frame 80 glows with agreen light when the associated module is operating in the signal path.When there is no fully-seated module in the associated recess frame, orwhen a fully-seated module is bypassed by any of the switches, the lightemitting diode 57 is dark and the light emitting diode 56 glows with ared light.

Light emitting diode 59 glows with a green light when the system bypassswitch 58 and its associated foot switch 73 are not commanding systembypass. When the switches do command a system bypass, light emittingdiode 59 is dark and light emitting diode 60 glows with a red light.

Output level is adjusted with potentiometer 63 and is indicated by theillumination pattern of light emitting diodes 65. The output audiosignal, having been modified according to the effects selected, ispresent at an output jack at the rear of the main housing.

FIG. 11 shows a front view of a module 43 fully seated in a recess frame80. The module face shown in FIG. 11 is flush with the recess frame.Markings 96 on the face of the module identify the effect or name of thecircuit and identify control functions with control panel 70 of mainhousing 41. In this case "Phaser" is the name of the circuit. "Contour"has an arrow pointing toward potentiometer 50, "Accent" has an arrowpointing toward potentiometer 51, and "Speed" has an arrow pointingtoward potentiometer 45.

FIGS. 12, 13, 14, 15, and 16 show one embodiment of the structure ateach recess of the main housing 41 of the system shown in FIG. 10. Therecess frame 80, the contact element holder 82, and the module 43 arerepeated at each recess. The printed circuit mother board 84 extendsessentially the full width of the main housing and electronic componentswith their interconnections being mounted there. The control panel 70also extends the full width of the main housing and mounts the controlsas described above. The contact element holder 82 is bolted to theprinted circuit mother board 84, and the recess frame 80 is bolted tothe contact element holder at its rear end and hooked into the controlpanel at its front end.

FIG. 12 shows pointed ends of recess contact elements 88 and how theycontact the eyelet-shaped module contact elements 90.

FIG. 13 shows three right angle bends in the recess contact elements 88.The contact elements befoe bending are approximately 4 cm. long, 0.3 cm.wide, and 0.08 cm. thick.

The material is high-strength beryllium copper or phosphor bronze,appropriately plated. The pointed end and approximately 0.8 cm. oflength are perpendicular to the rear face of the module. The first rightangle bend sends the element parallel with the rear face of the modulefor approximately 0.8 cm. It is this length that can bend, allowingtravel of the module after first contact of module contact elements 90and recess contact elements 88 and before the module is fully seated andlatched into the recess frame. The bending of all recess contactelements also provides a spring force to partially expel the module whenlatch-coupled switch 44 is operated for that purpose. After a secondbend the recess contact element passes through a slot (92 of FIG. 16) inthe contact element holder and through the printed circuit mother board.After passing through the mother board the third bend takes the recesscontact element parallel to the mother board where it is soldered 81 toa metallic connecting trace on the mother board.

FIG. 13 also shows the latch-coupled switch 44, and latch 86 in themodule notch 98, locking in the module. Latch-coupled switch 44 andlatch 86 operate mechanically in the same fashion as switch 4 and latch25 as described in connection with FIG. 7.

FIG. 14 essentially shows the back view of a partially-inserted moduleseen from the rear of the recess frame. Module contact elements 90 areshown as eyelets. Inside the module, jumper wires are soldered to theeyelets at one end and to the module printed circuit board at the other.

FIG. 15 essentially shows the front view of an empty recess. FIG. 16essentially shows the front view of an empty recess with recess frame 80removed. The contact element holder 82 is shown holding the recesscontact elements 88.

FIG. 17 shows an electrical block diagram, partly schematic, of theadvanced audio signal processing system of FIG. 10. Recess contactelements, all denominated as 88 in mechanical drawings above, are heregiven suffix numbers to enable the description of their variouselectrical connection. For convenience, the logical "0" will beconsidered as the presence of a voltage -E and the logical "1" as theessential absence of any voltage, or ground level.

When the voltage -E appears at the control input 138 of the electronicswitch, the input to the electronic switch 130 is essentially connectedto line 132 and the input of a module at contact element 128. The outputof the electronic switch 136 is essentially connected to line 134 andthe output of the module at contact element 101. Thus the main signalpath proceeds through the module and the module is operative. Whenground level voltage appears at the control input 138 of the electronicswitch, the input of the electronic switch 130 is essentially connectedto the output of the electronic switch 136, and the main signal pathproceeds directly through the electronic switch and past the recesswithout regard to a module that could be fully seated in the recess.

To obtain voltage -E at 138, ground levels must be present at both 140and 142, the inputs to the NAND gate. As can be seen, obtaining groundlevel at 140 requires both that latch-coupled switch 44 be closed andthat contact elements 113 and 116 be connected. The switch 44 is closedwhen a module is fully seated in the recess and when the recess is fullyempty. Connection between contact elements 113 and 116 is made only whena module is far enough into the recess for the jumper wire in the moduleto make a connection between contact elements 113 and 116. Thus groundlevel at 140 is obtained when, and only when, a module is fully seatedor fully inserted in the recess, i.e., when the module is fully matedwith the recess.

To obtain ground level at 142, either module bypass switch 48 or itsassociated foot switch 72 must be closed. In addition, either systembypass switch 58 or its associated foot switch 73 must be closed.

A conventional AC to DC power supply is shown supplying both positiveand negative voltages to all modules at contact elements 114 and 115 andto the main housing circuitry. The voltage levels represent a designchoice in relation to the electronic components selected.

An envelope follower produces a voltage proportional to signal level.The voltage is supplied to all modules at contact element 129. Modulesuse this voltage to modify various prameters as a function of signallevel. The input level indicator circuits also use this voltage.Provision is made, with switch 53, for the modules to receive anexternally supplied voltage as an alternative.

FIG. 18(a) shows a simplified electronic switch for relation to theelectronic switch in FIG. 17. When voltage -E is present at 138 and atthe gates of field effect transistors Q2 and Q3, the transistors areconductive from source to drain, and input 130 is effectively connectedto 132, and output 136 is effectively connected to 134. Because voltage-E is present at 138, ground level is present at 144 and the gate of Q1.Q1 is thus effectively open from source to drain. Conversely when groundlevel is present at 138, Q2 and Q3 are open, Q1 is conductive, and input130 is effectively connected to output 136.

FIG. 18(b) shows a preferred electronic switch for use with FIG. 17. Q2has been found to be unnecessary when mixing amplifiers with a lowoutput impedance are used as shown. Thus the module input is directlyconnected to the signal path. Module output is connected to the signalpath through the electronic switch at the same time the bypass is openedand vice versa. R-C time delays are used to tailor the break-before-makecharacteristic of the switch. A module level control potentiometer 49adjusts system level at this point but only when the module isoperative.

FIGS. 19 through 23 show representative and existing art circuitry foruse in the audio effects circuit modules for use in the systemsdescribed herein. The figures have recess contact element suffix numbersso they can be directly related to FIG. 8, FIG. 17, and FIG. 26. Thereare many other existing circuits that can be used, and circuits yet tobe designed may also be used.

FIG. 19 shows a tone control circuit that can raise and lower the levelof both the upper and lower end of the audio spectrum. Power is suppliedat terminals 114, 115, and 116. All modules connect terminals 113 and116 together as described above, although this connection is not used inthe basic system of FIG. 1. Potentiometer 52 and 45 control the boostand cut of treble and bass of this audio effect circuit module. They arelocated on the control panels, 30 and 70, and shown in FIGS. 8 and 17.The triangle-shaped figure with "IC" inside represents an integratedcircuit operational amplifier as supplied by multiple vendors. Thedesign choice of exactly which amplifier to select relates to choice ofpower supply voltages and other design considerations.

FIG. 20 shows a "fuzz" or controlled distortion circuit. The signal inthe amplitude-versus-time domain is clipped, harmonics are created, and"sustain" is increased when processing a percussive signal such as thatproduced by a guitar.

FIG. 21 shows a swept audio filter circuit. The resonant frequency ofthe filter varies depending on signal level as supplied by the envelopefollower.

FIG. 22 shows a tremolo circuit. The gain through the circuit is variedlinearly at an adjustable rate.

FIG. 23 shows a noise gate circuit. When the envelope follower voltageexceeds a threshold, the audio signal passes, otherwise not.

FIG. 1, FIG. 10, and FIG. 24 illustrate the use of four module-receivingrecesses, but a unit can be constructed containing any feasible numberof module-receving recess, with even a one-recess system havingpractical applications.

An alternative embodiment of an advanced audio signal processing systemshowing two features which may be incorporated therein is illustrated inFIGS. 24 through 28. The same elements of the previous system describedin FIG. 10 are shown having the same number of designations thereon asearlier described, with the different elemetns of the alternativeembodiments being set forth with more particularity hereinbelow.

As more particularly illustrated in FIG. 26, the circuitry oflatch-coupled switch 44 has been removed from the system, and detectingmeans 288 for detecting the fully-mated position or condition of thecontact elements 88 and 90 has been provided as shown in FIG. 28. Theposition detecting means 288 is constructed such that it is the lastrecess contact element to make contact with the module contact element90 upon insertion of the module, and the first contact element to breakcontact with the module contact elements upon removal of the module. Ina preferred embodiment, the contact element 288 is constructed to beshorter than the remaining recess contact elements 88 as shown in FIG.28. In another embodiment, not shown, the recess contact elements 88could be the same length, and the respective module contact elementcould be recessed in the module an appropriate distance, such that thelast-to-make first-to-break characteristic of the position detectingmeans is provided. By providing this modification, the circuitry oflatch-coupled switch 44 can be deleted from the system circuit, as shownin FIG. 26. Recess contact element 113 corresponds to the recess contactelement 288, which is shown in FIG. 28.

In other words, to obtain voltage -E at 138, ground levels must bepresent at both lines 140 and 142, the respective inputs to the NANDgate. Obtaining ground level at 140 requires only that contact elements113 and 116 be connected, since the circuitry of latch-coupled switch 44is no longer in the circuit. The connection, if made last, would providethe same result as that obtained with the circuit shown in FIG. 10utilizing the latch-coupled switch 44. The structure illustratedhereinabove with respect to a shorter contact element ensures that theconnection between recess contact elements 113 and 116, as provided bythe jumper in the module, be made last. Upon insertion of the module,the contact elements 113 and 116 would be made only when a module is farenough into the recess for the jumper wire and the module to make aconnection between said detecting contact elements, and which onlyoccurs when a module is fully mated with the remaining module contactelements 90 and recess contact elements 88, i.e., when the module isfully mated with the recess. In other words, the audio signal is routedthrough the recess only after the position detecting means has indicatedthat the fully-mated condition exists and therefore noiseless routingthrough the module by the electronic switch is in response to the signalsent by the position detecting means.

Likewise, upon removal of the module, the shorter contact element 288 isstructured so that it is the first contact to break electrical contactupon removal of the module, before the heretofore established electroniccontact between the module contact elements 90 and recess contactelements 88 is disturbed. Once the electronic contact is broken atcontact elements 288 and 90, the connection between terminals 113 and116 is broken such that the ground level is no longer present at NANDgate input 140. At that time, since voltage -E at 138 is no longerpresent, the electronic switch operates as previously described to routethe signal past the recess, i.e., directly through electronic switch 130to 136 as shown in FIG. 26.

Another feature, as more particularly shown in FIGS. 24, 27, and 28, isthat the controls may be positioned on the module and interact withinthe circuitry of the audio effects circuit module itself, rather than,or in addition to, being associated with the controls shown on thecontrol panel. Although the module control circuitry is not shown,conventional control circuitry would be applicable, and the exampleshown in FIG. 27 with respect to a phaser shows that the speed, contour,and accent of the phaser sound effects module could be controlled by thecontrols 256. Although the embodiment shown for the controls comprisesknobs, a thumb wheel arrangement for the control could likewise beutilized, and, if desired, the controls themselves could be indented orrecessed within the face of the module so as to prevent unwanted bumpingor movement of the desired module control setting.

Another embodiment, as shown in FIG. 29, is that the recesses, althoughdisclosed hereinbefore as being in series, could be electricallyconnected in parallel in the system. In another embodiment which couldlikewise be utilized in accordance with the present invention, therecesses may be connected as a network of series-parallel combinationsof recesses. As shown in FIG. 30, the recesses may comprise one or morerecesses connected in series, which are then collectively connected inparallel to provide different audio effects, depending on the modulesselected and inserted within each recess, and their order. For example,as shown in FIG. 30, recesses 1,2, and 3, are connected in series, asare recesses 4,5, and 6. The networks are then connected in parallelwith a recess 7, which collectively operate to serve as the main audiosignal output.

Although particular embodiments of the invention have been described andillustrated herein, it is recognized that modifications and variationsmay readily occur to those skilled in the art and consequently, it isintended that the claims be interpreted to cover such modifications andequivalents.

What is claimed is:
 1. An electronic system for operatively inserting atleast one audio effects circuit module into a main audio path having asource audio signal, comprising:a main housing having an audio signalinput, and an audio signal output associated with the audio signal pathfor carrying the source audio signal between said input and said output;at least one audio effects circuit module for modifying audio signals,said module having a plurality of electrical contact elements; said mainhousing further having at least one module receiving recess forreceiving and releaseably engaging said module, said recess havingcorresponding electrical contact elements for mating with said modulecontact elements in a fully engaged position; and recess switching meansassociated with said recess, said switching means including means forconnecting the main audio path together between an input and output ofsaid receiving means, said switching means further including means forbreaking the audio path between said recess input and output and forrouting said audio signal through said module only when said modulecontact elements are fully mated with said recess contact elements,wherein said recess switching means includes position detecting meansfor detecting when said module is in a fully-mated position in saidrecess and for providing a control signal, and wherein said recessswitching means includes electronic switching means in said audio signalpath associated with said recess for routing said audio signal throughsaid module in response to said control signal.
 2. The system of claim 1wherein said position detecting means includes a detecting contactelement comprising one of said recess contact elements being positionedwith respect to the remaining recess contact elements so that saiddetecting contact element is the last to make contact with said modulecontact elements upon insertion of said module, and the first to breakcontact with said module contact elements upon removal of said module.3. The system of claim 1, wherein said position detecting means includesa detecting contact element comprising one of said module contactelements being positioned with respect to the remaining module contactelements so that said detecting contact element is the last to makecontact with said recess contact elements upon insertion of said module,and the first to break contact with said recess contact elements uponremoval of said module.
 4. The system of claim 1, wherein there is aplurality of recesses and associated recess switching means beingconnected in series.
 5. The system of claim 1, wherein there is aplurality of recesses and associated recess switching means beingconnected in parallel.
 6. The system of claim 1, wherein there is aplurality of sets of recesses and associated recess switching meansbeing connected in parallel, each of said sets comprising at least onerecess and associated recess switching means being connected in series.7. The system of claim 1, wherein said recess switching means includesan electronic switch having time delay circuits connected between acontrol input, said audio signal output, and said recess contactelements.